Knee joints are required to have functionalities under the severest mechanical environment rather than characteristics of the surface shape of the joints and the degree of freedom for joint motions. Important functions such as load transmission and shock absorption are assumed by a meniscus.
The meniscus exists between the femur and the tibia to assume the action of dispersing the load applied from the femur for absorbing shocks and the role of providing stability and smooth motions of the knee joint. The meniscus is formed of fibrocartilage and collagen and is supplied with blood circulation from the surrounding joint capsules and with nutrients from synovial fluid.
For the treatment of meniscal disorders involving damages to or degeneration of the menisci, restoration of its mechanical functionalities is important. Conservative treatments (such as casting and bracing) or surgical treatments (such as suture and excision) are performed on restorable disorders, while, for unrestorable disorders, since the meniscus may not be regenerated, allogenic meniscal implantation as reported in Europe and the United States and regeneration medicine recently attracting attention (meniscus regeneration measures for regenerating the meniscus by the use of cultured cells from the meniscus to fill it) have been suggested. However, for meniscal implantation, it is highly difficult to obtain menisci in our country and, also for regeneration medicine, it has not yet been put into practical use as of this moment and is expected to require a great deal of time and cost to reach regeneration.
As such, the advent of artificial menisci is much anticipated. As described above, however, since between the joints is where the severest mechanical environment is found in an organism, materials capable of withstanding such severe environment do not exist at the moment. In addition, moderate mechanical properties for an extended period of time must be maintained for application in an organism for an extended period of time and also any osteoarthritis must not be induced. Therefore, the present invention aims to provide, primarily, actually usable, artificial menisci for the first time and, secondarily, artificial menisci which, when applied for an extended period of time in an organism, can maintain moderate mechanical properties for an extended period of time and will not induce any osteoarthritis.